Definition: In this task, you are given an input list A. You need to convert all the alphabets in the list with a number representing their position in the English alphabet. E.g., replace A by 1, B by 2, a by 1, b by 2, and so on.
Input: ['3139', 'E', '8721', 'H', 'g', 'H', '9931', 'b']

3139, 5, 8721, 8, 7, 8, 9931, 2